Although I havn't tried using it with the squad I usually play with, I had an idea for giving North/East/South/West directions on Rush maps.

For each pair of Mcoms, there is generally a main road / path going through the middle of them both. North would be designated as the line from your spawn, through this path between the Mcoms.

On most maps this is obvious , for example Valparaiso it's always a straight line to the next MComs. On some maybe not so obvious like laguna presa where you would simply take the main road leading to the MCOM instead of starting at your spawn.